The present invention generally relates to a liquid level sensor and, in particular, relates to such a sensor which is remotely capable of providing a continuous indication of the level of a liquid.
The determination of the level of a liquid is required in a wide variety of circumstances. One field wherein such a determination is frequently required is the field of analytical instruments. For example, in many types of analysis it is necessary to provide the user of an instrument with the capability of performing measurements at rather low temperatures. One manner of providing such low temperatures is by use of coolants such as, for example, liquid nitrogen. In most instances the coolants are kept in a Dewar flask or some other similarly constructed insulated reservoir.
Conventionally, the liquid level is monitored by a plurality of liquid presence sensors strategically positioned within the reservoir. For example, three sensors, one near the highest point, one at the half-full point and one near, or on, the bottom, are usually considered sufficient.
However, with the advent of computerized controlled analysis it has become increasingly important to monitor the amount of coolant available. The importance has increased since, if an analysis is being performed on a plurality of samples or if a plurality of tests are being performed on a single sample, the test results may become compromised if the analysis is interrupted to replenish the coolant. Under such circumstances it is almost a necessity to continuously monitor the coolant level to ensure that sufficient coolant is available for a given series of tests. Naturally, any thermal equilibrium achieved would be destroyed by adding coolant to the reservoir during the analysis.